<html>
<head>
<script type="text/javascript">
function alertValue()
  {
  var x=document.getElementById("mySelect").selectedIndex;
  alert(document.getElementsByTagName("option")[x].value);
  }
</script>
</head>
<body>

<form>
Select your favorite fruit:
<select id="mySelect">
  <option value="apple">Apple</option>
  <option value="orange">Orange</option>
  <option value="pineapple">Pineapple</option>
  <option value="banana">Banana</option>
</select>
<br /><br />
<input type="button" onclick="alertValue()" value="Alert selected value">
</form>

</body>
</html>